Question: What do the following two equations represent? $5x+2y = -4$ $-8x+20y = -3$
Solution: Putting the first equation in $y = mx + b$ form gives: $5x+2y = -4$ $2y = -5x-4$ $y = -\dfrac{5}{2}x - 2$ Putting the second equation in $y = mx + b$ form gives: $-8x+20y = -3$ $20y = 8x-3$ $y = \dfrac{2}{5}x - \dfrac{3}{20}$ The slopes are negative inverses of each other, so the lines are perpendicular.